Length Control System and Method

ABSTRACT

A retractable leash device (e.g., for pets, children, or the like) having a length control system for limiting the extendable length of a main line is provided. The device includes a cover plate mounted on a wind-up spool and having at least one ridged channel that interacts with a length control switch during line extension to control the extendable length of the main line while simultaneously maintaining the retractability of the main line.

FIELD OF TECHNOLOGY

The present technology relates to length control systems, and more particularly, to retractable leash devices (e.g., for pets, children, or the like) in which the extendable length of a line therein is shortened without affecting its retractability.

BACKGROUND

The retractable nature of conventional leashes benefits the user by eliminating the excess line that can accumulate when the distance between the user and the leashed being (e.g., pet) varies. These devices feature a housing with a handle portion that encloses a wind-up spool biased to retract an attached fixed length of line. The wind-up spool extends out line when pulled and retracts the line when tension is lessened. The maximum travel of the line in current devices can be limited by the user in two ways: (1) by fully extending the line on the wind-up spool, thus reaching the maximum length of the leash; and (2) by employing a manually actuated brake mechanism, which locks and fixes the wind-up spool to a set length the user desires. A locking mechanism on the brake allows the user to lock in place the wind-up spool without the user having to apply constant pressure to the brake mechanism.

Improvements to retractable leashes are desirable, one benefit of the present technology is to provide a new and improved retractable leash. Conventionally, if a user desires to shorten the length of the retractable leash, the user typically employs a manually actuated brake that can be either locked or held in place manually by applying constant pressure. Shortening the length of the leash is beneficial in situations where the user desires the pet or other animal or object connected to the leash to remain closer so that the user has more control. Shortening the leash can be beneficial when the user is in an area with potential hazards, such as vehicle or bicycle traffic, steep drop-offs or cliffs, other animals or people nearby, and other potential dangers. Shortening the leash by means of the brake mechanism, however, freezes the wind-up spool and eliminates the retractable nature of the device, which can result in the accumulation of excess line in the leash when the distance between the user and the pet is lessened, thereby negating the benefit of the device itself. The accumulated excess line caused by this situation can be dangerous, potentially presenting a tripping hazard to the user, the pet, or nearby pedestrians. The accumulated line can also become tangled in the pet's feet, forcing the user to halt his or her activity to untangle the line. Thus, a need exists for a leash in which a user can have more control over its length, for ease of use.

SUMMARY OF THE TECHNOLOGY

The claimed technologies are (1) a length control system, (2) a retractable leash device in which the length control system is enclosed in a housing, (3) and a method for restricting the movement of a human or animal using the length control system. The length control system is comprised of a spool with two opposing parallel surfaces, a center portion joining the two surfaces; an extendable and retractable main line coiled around the center portion of the spool; a channel defined on one of the two spool surfaces or on a cover plate affixed to one of the two spool surfaces; and a switch configured to interact with the channel to restrict the extension but not the retraction of the main line. In some embodiments this length control system can be enclosed in a housing to form a retractable leash device. This retractable leash device can be used in the claimed method to restrict the distance that a leashed being can travel from the leash holder without restricting the retractabilitiy of the leash's main line.

BRIEF DESCRIPTION OF THE DRAWINGS

The present technology is discussed in greater detail below with reference to exemplary embodiments illustrated in the accompanying drawings, in which:

FIG. 1 is a perspective view of a retractable leash device having a main line, in accordance with various embodiments of the present technology;

FIGS. 2a and 2b are plan views of a retractable leash device in a partially disassembled state, illustrating a switch in different positions of a channel of the device, in accordance with various embodiments of the present technology;

FIG. 3a is a side view of a retractable leash device, in accordance with various embodiments of the present technology;

FIG. 3b is a top view of a switch of a retractable leash device, in accordance with various embodiments of the present technology;

FIGS. 3c and 3d are side views of a switch, in accordance with various embodiments of the present technology;

FIG. 3e is a bottom view of a switch, in accordance with various embodiments of the present technology;

FIG. 3f is a plan view of a side surface of a wind-up spool of a retractable leash device, in accordance with various embodiments of the present technology;

FIGS. 4a-8b illustrate the progressing interaction between a switch and a channel during extension and retraction of a main line, in accordance with various embodiments of the present technology;

FIG. 9a is a side view of a retractable leash device, in accordance with various embodiments of the present technology;

FIG. 9b is a top view of a switch of a retractable leash device, in accordance with various embodiments of the present technology;

FIGS. 9c and 9d are side views of a switch, in accordance with various embodiments of the present technology;

FIG. 9e is a bottom view of a switch, in accordance with various embodiments of the present technology;

FIG. 9f is a plan view of a side surface of a wind-up spool of the retractable leash device, in accordance with various embodiments of the present technology;

FIGS. 10a-12b illustrate a switch in various positions with respect to various channels of a retractable leash device, in accordance with various embodiments of the present technology;

FIG. 13a is a side view of a retractable leash device, in accordance with various embodiments of the present technology;

FIG. 13b is a top view of a switch of a retractable leash device, in accordance with various embodiments of the present technology;

FIGS. 13c and 13d are side views of a switch, in accordance with various embodiments of the present technology;

FIG. 13e is a bottom view of a switch, in accordance with various embodiments of the present technology;

FIG. 13f is a plan view of a side surface of a wind-up spool of the retractable leash device, in accordance with various embodiments of the present technology; and

FIGS. 14a-16b illustrate a switch in various positions with respect to various channels of a retractable leash device, in accordance with various embodiments of the present technology.

DETAILED DESCRIPTION

As used herein, the term “leash” refers to any device having a length, such as a strap or cord, that can be used to restrain a human or animal, including but not limited to a pet or a child. As used herein, the term “retractable” means having a length that can be moved away from, or towards, a stationary point in a manner that adjusts the distance between the stationary point and a point along the length. FIG. 1 is a perspective view of a retractable leash device 100 in accordance with various embodiments of the present technology. FIGS. 2a and 2b are views of retractable leash device 100 in a partially disassembled state, illustrating a switch 154 in different positions of a channel 152 of the device, in accordance with various embodiments of the present technology. Retractable leash 100 can include a housing 101 composed of opposite housing sides that, when coupled to one another, form a wind-up spool enclosure portion 101 a and a handle portion 101 b. The housing sides can be secured to one another by conventional means, e.g., via one or more screws or snaps. The second housing side can include one or more holes on an inner face thereof that align with one or more corresponding holes on an inner face of the first housing side for attachment by screws. One or more of the holes of the second housing side can include threads for coupling to corresponding threads of screws, or vice versa.

Referring to FIGS. 1, 2 a, and 2 b, a wind-up spool 140 can be mounted, via a center hole 142, to a column 105 protruding from the inner face of the second housing side. A main line 160 can have an end 160 e, and can be coiled about wind-up spool 140. End 160 e can be coupled to a connector 165, which can, in turn, be coupled to an extension line 166 (e.g., for connecting to a collar, harness, or other restraining system for a subject, e.g, an animal, such as a pet or the like) via a link 167. Connector 165 can serve as a stopper that prevents end 160 e of main line 160 from retracting into housing 101. Retractable leash 100 can also include a spring or spring-like mechanism (not visible in the drawing figures) that provides a constant recoil force for retracting main line 160 whenever it is extended from wind-up spool 140.

Retractable leash 100 can also include an optional brake mechanism 170 having a manually actuated brake switch 172 and brake leg 174. When actuated, brake leg 174 can provide frictional forces upon contact thereof with portions of wind-up spool 140 (e.g., with side surfaces of wind-up spool 140, such as side surface 144), which can prevent retraction and extension of main line 160.

To maintain the retractability of main line 160, while simultaneously limiting the extendable length thereof, retractable leash device 100 can advantageously include a length control system. In various embodiments, the length control system can include a channel 152 and a switch 154 that interacts with channel 152. As used herein, “interacts with” means that a portion or all of the switch contacts a portion of the channel in a manner that is secure but also can slide freely along the length of the channel upon application of mechanical force. Channel 152 can be defined in a cover plate 150 that is mounted to side plate 144 of wind-up spool 140. Channel 152 (which can be, e.g., a ridged channel) can be defined as a spiral-like curve that extends concentrically outward from an inner channel end 152 a (disposed in a region adjacent the center hole) to an outer channel end 152 b (disposed in a region proximate the periphery of cover plate 150). In various embodiments, portions of the curve can be equidistant from one another (e.g., by a distance R), or of varying distances from each other, as it spirals from end to end. Cover plate 150 can be made of any suitable material (e.g., metal, plastic, or the like), and can be mounted in any suitable manner (e.g., via an adhesive, with one or more clips crews or snaps, or the like). Cover plate 150 can conform to the circular shape of side plate 144, and can include a center hole 151 that aligns with center hole 142 of wind-up spool 140 for mounting to column 105. However, cover plate 150 can alternatively not include a center hole. For example, in some embodiments, the depth of wind-up spool 140 can span the entirety of (or even exceed) the height of column 105, in which case, there is no need for cover plate 150 to have a center hole.

Switch 154 (which can, e.g., be a pin, a nail, or the like) can include a head and a post. The post can be constructed to pass through a length control slot 103 on the first housing side, which can be positioned to externally expose portions of channel 152. When the post is inserted through slot 103 and into channel 152, any extension or retraction of main line 160 can cause wind-up spool 140 and cover plate 150 to rotate, and thus channel 152 to also rotate with respect to the post. In the case of main line extension, channel 152 can traverse the post from channel end 152 b to channel end 152 a. Put another way, the post can traverse channel 152 from channel end 152 b to channel end 152 a. Conversely, in the case of main line retraction, the post can, for example, traverse channel 152 from channel end 152 a to channel end 152 b. As illustrated FIGS. 1, 2 a, and 2 b, switch 154 can assume different positions in channel 152 (and can move in a generally downward direction in length control slot 103), when main line 160 is extended from housing 101. When switch 154 reaches channel end 152 a, movement of wind-up spool 140 may be halted, effectively limiting the maximum extendable length of main line 160. Having cover plate 150 disposed over side plate 144 of wind-up spool 140 can advantageously restrict switch 154 to interact only with channel 152. Side plate 144 can thus serve as a barrier between the switch's post and main line 160, effectively preventing switch 154 from contacting and/or interfering with extension and retraction of main line 160 during use of retractable leash device 100.

The width of channel 152 can be defined such that it is large enough to receive and guide the post of switch 154. Additionally, the width of channel 152 can be uniform throughout its entire length. However, the width may vary, and may assume different shapes. In various embodiments, channel 152 can also be smooth, such that the switch's post travels therein in unimpeded or with minimal frictional forces against the sides of the channel.

While switch 154 can limit the amount of main line 160 that can be extended from wind-up spool 140, it does not restrict or interfere with the retractability of main line 160 when it is released from an extended state. This is because, as the switch's post traverses in a direction from outer channel end 152 b to inner channel end 152 a during main line extension (that is, as wind-up spool 140 rotates from a position in which the post contacts outer channel end 152 b to a position in which the post contacts inner channel end 152 a), the post is free to conversely traverse in a direction from inner channel end 152 a to outer channel 152 b when main line 160 is subsequently released.

The amount of length of main line 160 that is permitted to extend from housing 101 can be at least partially controlled by the rotational position of cover plate 150 with respect to wind-up spool 140. For example, cover plate 150 can be rotationally positioned with respect to wind-up spool 140 such that, when main line 160 is fully retracted and connector 165 abuts (or is disposed proximate to) the slot through which main line 160 extends, the post of switch 154 abuts (or is disposed proximate to) channel end 152 b. In this configuration, main line 160 can be allowed to extend by a length approximately equal to the length of ridged channel 152 from channel end 152 b to channel end 152 a.

Alternatively, cover plate 150 can instead be rotationally positioned with respect to wind-up spool 140 such that, when main line 160 is fully retracted, the post of switch 154 is disposed at a distance from channel end 152 b. Here, main line 160 can be allowed to extend by a length shorter than the length of channel 152 (from channel end 152 b to the channel end 152 a), since the length of channel 152 that switch 154 can traverse during extension of main line 160 is shorter. In this way, depending on how wind-up spool 140 or cover plate 150 is oriented during manufacture, the preset extendable length of main line 160 provided by channel 152 can be different from the length of channel 152 itself.

In some embodiments, rather than being defined on cover plate 150, channel 152 can be defined directly onto side plate 144 of spool 140, rendering a cover plate, such as cover plate 150, unnecessary. In these embodiments, wind-up spool 140 and cover plate 150 can, in effect, comprise a single component. In these embodiments side plate 144 may be thicker, and its channel may not be defined through the entire thickness of the side plate, which can avoid the post of switch 154 contacting with main line 160, disposed on the opposite side of the side plate.

FIG. 3a is a side view of an alternate retractable leash device 200, in accordance with various embodiments of the present technology. FIG. 3b is a top view of a switch 254 of exemplary leash device 200. FIGS. 3c and 3d are side views of switch 254. FIG. 3e is a bottom view of switch 254. FIG. 3f is a plan view of a side surface 250 of a wind-up spool 240 of exemplary leash device 200.

Exemplary leash device 200 can include a housing 201 having opposite housing sides, a wind-up spool 240, a main line 260, and a connector 265. In various embodiments, the length control system can include a channel 252 and a switch 254. Switch 254 can be, for example, a manual switch mechanism that a user can displace by moving or flipping in certain directions.

Referring to FIG. 3f , in certain embodiments, channel 252 can be defined in a side surface 250 of wind-up spool 240. However, in certain embodiments, channel 252 can alternatively be defined in a cover plate mountable or mounted to a side surface 250 of spool 240. Channel 252 can include a channel end 252 a and a channel end 252 b having an entry area 252 c.

Referring to FIGS. 3b-3e , in certain embodiments, switch 254 can include a manual mechanism 254 m, a bottom frame 254 f having a guide path 254 g, a spring 254 s disposed in guide path 254 g, and a pin 254 p having a head 254 h disposed in guide path 254 g. As shown in FIG. 3e , spring 254 s, in its natural state, can apply a force to head 254 h of pin 254 p and can retain pin 254 p on one side of guide path 254 g. Referring to FIG. 3c , switch 254 can be disposed at a slot 203 such that movement of manual mechanism 254 m, disposed on an external side of housing 201, can cause pin 254 p, disposed on an internal side of housing 201, to traverse guide path 254 g.

The following description of how exemplary leash device 200 can be operated to limit the extendable length of main line 260, without affecting retractability of the line, is made with reference to FIGS. 4a-8b . FIGS. 4a-8b illustrate an exemplary progressing interaction between switch 254 and channel 252 during extension and retraction of main line 260 from housing 201. In particular, FIGS. 4a and 4b are views of exemplary leash device 200, illustrating the interaction between switch 254 and channel 252, when switch 254 is in an unactuated state and main line 260 has not yet extended from housing 201. FIGS. 5a and 5b are views of leash device 200, illustrating the interaction between switch 254 and channel 252, when switch 254 is in an actuated state and main line 260 has not yet extended from housing 201. FIGS. 6a and 6b are views of leash device 200, illustrating the interaction between switch 254 and channel 252, when switch 254 is in the actuated state and a certain amount of main line 260 has extended from housing 201. FIGS. 7a and 7b are views of leash device 200, illustrating the interaction between switch 254 and channel 252, when switch 254 is in the actuated state and main line 260 has extended from housing 201 to a preset length defined by the length of channel 252 between channel ends 252 a and 252 b.

Referring to FIGS. 4a and 4b , switch 254 is shown in its unactuated state and main line 260 is fully coiled about spool 240. In this embodiment, spring 254 s is in a relaxed state and applies force to pin 254 p, retaining pin 254 p at an upper portion of switch 254. In this position, no portion of pin 254 p is in contact with channel 252. Next, when switch 254 is actuated (e.g., via user operation of manual mechanism, 254 m), pin 254 p can compresses spring 254 s and enters entry area 252 c at channel end 254 b of channel 252 (FIGS. 5a and 5b ). After pin 254 p enters channel 252, any extension of main line 260 from housing 201 can cause the pin to traverse the channel. As a result, pin 254 p can also compress spring 254 s during the traversal. FIGS. 6a and 6b depict pin 254 p having traversed to a position in channel 252 between channel ends 252 b and 252 a, after main line 260 has extended from housing 201 by a certain amount. As main line 260 continues to extend, pin 254 p can continue to traverse channel 252 until it reaches channel end 252 a. At this point (FIGS. 7a and 7b ), pin 254 p can fully compress spring 254 s, traversal of pin 254 p is halted, and further extension of main line 260 is restricted. In this way, the length control system of leash device 200 can restrict extendibility of main line 260 to a preset amount that is less than the full length of main line 260 (see FIG. 7b , where an amount of main line 160 remains coiled about spool 240). However, the system does not prohibit retractability of main line 260 from the state shown in FIGS. 7a and 7b , since release of main line 260 can allow a spring mechanism coupled to spool 240 to return to its relaxed state, and thus draw the main line back into housing 201 and around the spool. As main line 260 is retracted, spool 240, and thus channel 252, continues to rotate, allowing pin 254 p to reverse its travel path from inner channel end 252 a to outer channel end 252 b. As pin 254 p reverses its travel in channel 252, spring 254 s can continually be decompressed. FIGS. 8a and 8b depict pin 254 p having reversed its traversal of channel 252 to a position between channel end 252 a and 252 b.

FIG. 9a is a side view of an alternate exemplary retractable leash device 300, in accordance with various embodiments of the present technology. FIG. 9b is a top view of a switch 354 of leash device 300. FIGS. 9c and 9d are side views of switch 354. FIG. 9e is a bottom view of switch 354. FIG. 9f is a plan view of a side surface 350 of a wind-up spool 340 of leash device 300.

Exemplary leash device 300 can include a housing 301 having opposite housing sides, a wind-up spool 340, a main line 360, and a connector 365. In various embodiments, the length control system can include multiple channels 352 a, 352 b, and 352 c, and a switch 354.

Referring to FIG. 9f , in certain embodiments, channels 352 a-c can be defined in a side surface 350 of wind-up spool 340. However, in certain embodiments, channels 352 a-c can alternatively be defined in a cover plate mountable or mounted to a side surface 350 of spool 340. Channels 352 a-c can be connected to one another via a bridge 399. In certain embodiments, channel 352 a can be circular, and channels 352 b and 352 c can be spiral-like. Given channel 352 a's circular shape, it is merely a continuous circular path. Channel 352 b can have a channel end b1 and a channel end b2, and channel 352 c can have a channel end c1 and a channel end c2.

Referring to FIGS. 9b-9e , in certain embodiments, switch 354 can include a manual mechanism 354 m, a bottom frame 354 f having a guide path 354 g, a spring 354 s disposed in guide path 354 g, and a pin 354 p having a head 354 h disposed in guide path 354 g. As shown in FIG. 9e , spring 354 s, in its natural state, can apply a force to head 354 h of pin 354 p and can retain pin 354 p on one side of guide path 354 g. Referring to FIG. 9c , in certain embodiments switch 354 is disposed at a slot 303 such that movement of manual mechanism 354 m, disposed on an external side of housing 301, can cause pin 354 p, disposed on an internal side of housing 301, to traverse guide path 354 g.

The following description of how exemplary leash 300 can be operated to limit the extendable length of main line 360, without affecting retractability of the line, is made with reference to FIGS. 10a-12b . FIGS. 10a-12b illustrate the interaction between switch 354 and channels 352 a-c during extension and retraction of main line 360 from housing 301. In particular, FIGS. 10a and 10b are views of leash device 300, illustrating the position of switch 354 with respect to bridge 399 and channel 352 a, when switch 354 is in an unactuated state and main line 360 has not yet been extended from housing 301. In this position and in its unactuated state, any extension of main line 360 will merely cause pin 354 p to traverse channel 352 a in circles—channel 352 a does not restrict the extension of the main line.

FIGS. 11a and 11b are views of leash device 300, illustrating the interaction between switch 354, bridge 399, and channel 352 b, when switch 354 is in an actuated state in a direction −X, and main line 360 has not yet been extended from housing 301. When switch 354 is actuated in the −X direction and main line 360 is being extended, pin 354 p applies a force to spring 354 s in the +X direction and traverses channel 352 b, beginning at end b1, until the pin reaches end b2. At this point, further extension of main line 360 is prevented. In this way, the length control system of leash device 300 can restrict extensibility of main line 360 to a preset amount that is less than the full length of main line 360. However, the system does not prohibit retractability of main line 360 when pin 354 p is disposed at end b2, since release of main line 360 would allow a spring mechanism coupled to spool 340 to return to its relaxed state, and thus draw the main line back into housing 301 and around the spool. As main line 360 is retracted, spool 340, and thus channel 352 b, continues to rotate, allowing pin 354 p to reverse its travel path from end b2 to end b1. As pin 354 p reverses its travel in channel 352 b, spring 354 s is continually relaxed.

FIGS. 12a and 12b are views of leash device 300, illustrating the interaction between switch 354, bridge 399, and channel 352 c, when switch 354 is in an actuated state in a direction +X, and main line 360 has not yet been extended from housing 301. When switch 354 is actuated in the +X direction and main line 360 is being extended, pin 354 p applies a force to spring 354 s in the +X direction and traverses channel 352 c, beginning at end c1, until the pin reaches end c2. At end c2, further extension of main line 360 is prevented. However, because channel 352 c is longer than 352 b, the length control system of leash device 300 can restrict extendibility of main line 360 to a preset “intermediate” amount that is less than the full length of main line 360, but more than the preset length set by channel 352 b. Additionally, the system does not prohibit retractability of main line 360 when pin 354 p is disposed at end c2, since release of main line 360 would allow a spring mechanism coupled to spool 340 to return to its relaxed state, and thus draw the main line back into housing 301 and around the spool. As main line 360 is retracted, spool 340, and thus channel 352 c, continues to rotate, allowing pin 354 p to reverse its travel path from end c2 to end c1. As pin 354 p reverses its travel in channel 352 c, spring 354 s is continually relaxed.

FIG. 13a is a side view of an alternate exemplary retractable leash device 400, in accordance with various embodiments of the present technology. FIG. 13b is a top view of a switch 454 of leash device 400. FIGS. 13c and 13d are side views of switch 454. FIG. 13 e is a bottom view of switch 454. FIG. 13f is a plan view of a side surface 450 of a wind-up spool 440 of leash device 400.

Exemplary leash device 400 can include a housing 401 having opposite housing sides, a wind-up spool 440, a main line 460, and a connector 465. In various embodiments, the length control system can include multiple channels 452 a, 452 b, and 452 c, and a switch 454. As illustrated in FIG. 13f , channel 452 a is wider than the other channels. In certain embodiments, however, all the channels can have values within about 5% of each other.

Referring to FIG. 13f , channels 452 a-c can be defined in a side surface 450 of wind-up spool 440. However, in certain embodiments, channels 452 a-c can alternatively be defined in a cover plate mountable to a side surface 450 of spool 440. Channels 452 a-c can be connected to one another via a bridge 499. Channel 452 a can be circular, and channels 452 b and 452 c can be spiral-like. Given channel 452 a's circular shape, it is merely a continuous circular path. Channel 452 b can have a channel end d1 and a channel end d2, and channel 452 c can have a channel end e1 and a channel end e2.

Referring to FIGS. 13b-13e , in certain embodiments, switch 454 can include a manual mechanism 454 m, a bottom frame 454 f having a guide path 454 g, a spring 454 s disposed in guide path 454 g, and a pin 454 p having a head 454 h disposed in guide path 454 g. As shown in FIG. 13e , spring 454 s, in its natural state, can apply a force to the head of pin 454 p and can retain pin 454 p on one side of guide path 454 g. Referring to FIG. 13c , in certain embodiments switch 454 is disposed at a slot 403 such that movement of manual mechanism 454 m, disposed on an external side of housing 401, can cause pin 454 p, disposed on an internal side of housing 401, to traverse guide path 454 g.

In addition to pin 454 p, switch 454 can include an second pin 554. Second pin 554 can, for example, have a head and a post. In certain embodiments, second pin 554 can be fixed in place relative to frame 454 f. When manual mechanism 454 m is moved, second pin 554 can, along with pin 454 p, move in a corresponding manner or can move independently of each other.

The following description of how exemplary leash 400 can be operated to limit the extendable length of main line 460, without affecting retractability of the line, is made with reference to FIGS. 14a-16b . FIGS. 14a-16b illustrate the progressing interaction between switch 454 and channels 452 a-c during extension and retraction of main line 460 from housing 401. In particular, FIGS. 14a and 14b are views of leash device 400, illustrating the position of switch 454 with respect to bridge 499 and channel 452 a, when switch 454 is in an unactuated state and main line 460 has not yet been extended from housing 401. In this position and in its unactuated state, any extension of main line 460 will merely cause pin 454 p and second pin 554 to traverse channel 452 a in circles—channel 452 a does not restrict the extension of the main line.

FIGS. 15a and 15b are views of leash device 400, illustrating the interaction between switch 454, bridge 499, and channel 452 c, when switch 454 is in a first actuated state in a direction +X, and main line 460 has not yet been extended from housing 401. When switch is actuated in the +X direction and main line 460 is being extended, pin 454 p applies a force to spring 454 s in the +X direction and traverses channel 452 c, beginning at end e1, until the pin reaches end e2. At this point, further extension of main line 460 is prevented. During this time, second pin 554 remains in channel 452 a and traverses the channel in circles. In this way, the length control system of leash device 400 can restrict extensibility of main line 460 to a preset amount that is less than the full length of main line 460. However, the system does not prohibit retractability of main line 460 when pin 454 p is disposed at end e2, since release of main line 460 would allow a spring mechanism coupled to spool 440 to return to its relaxed state, and thus draw the main line back into housing 401 and around the spool. As main line 460 is retracted, spool 440, and thus channel 452 c, continues to rotate, allowing pin 454 p to reverse its travel path from end e2 to end e1. As pin 454 p reverses its travel in channel 452 b, spring 454 s is continually relaxed.

FIGS. 16a and 16b are views of leash device 400, illustrating the interaction between switch 454, bridge 499, and channel 452 c, when switch 454 is in a second actuated state in a direction −X, and main line 460 has not yet been extended from housing 401. When switch 454 is actuated in the −X direction, second pin 554 enters channel 452 b and pin 454 p remains in channel 452 a. When main line 460 is being extended, second pin 554 traverses channel 452 b, beginning at end d1, until the pin reaches end d2. At this point, further extension of main line 460 is prevented. Because channel 452 b is shorter than 452 c, the length control system of leash device 400 can restrict extendibility of main line 460 to an amount less than full length of main line 460 and less than the preset length set by channel 452 c. Additionally, the system does not prohibit retractability of main line 460 when second pin 554 is disposed at end d2, since release of main line 460 would allow a spring mechanism coupled to spool 440 to return to its relaxed state, and thus draw the main line back into housing 401 and around the spool. As main line 460 is retracted, spool 440, and thus channel 452 b, continues to rotate, allowing second pin 554 to reverse its travel path from end d2 to end d1. In certain embodiments, second pin 554 can remain in channel 452 b until manual mechanism 454 m is displaced in the +X direction.

In certain embodiments, channels 454 a and 454 b can be separate from channel 454 c, with no portion bridging channel 454 c to the other the channels. In these embodiments, second pin 554 can be a separate component from switch 454, and can be insertable into and retrievable from channel 452 b through slot 403 as desired by a user.

Accordingly, embodiments of the retractable leash device advantageously limits the extendable length of the main line, without affecting its retractability.

It will thus be seen that the aspects, features and advantages made apparent from the foregoing are efficiently attained and, since certain changes may be made without departing from the spirit and scope of the technology, it is intended that all matter contained herein shall be interpreted as illustrative and not in a limiting sense. 

What is claimed is:
 1. A length control system comprising: a spool comprising (a) two opposing surfaces, substantially parallel to each other and rotatable around an axis, and (b) a center portion joining the two surfaces; a main line coiled around the center portion of the spool and extendable and retractable; a channel defined on one of the two surfaces; and a switch configured to interact with the channel during extension or retraction of the main line from the spool, thereby restricting the extension of the main line to a predetermined length without restricting the retractability of the main line.
 2. The system of claim 1, wherein the length control system comprises two channels defined on one of the two surfaces.
 3. The system of claim 1, wherein the length control system comprises three channels defined on one of the two surfaces.
 4. The system of claim 1, wherein the switch is a pin configured to be inserted into the channel.
 5. The system of claim 1, wherein the switch is a manual switch mechanism.
 6. The system of claim 1, further comprising a manually actuated brake mechanism.
 7. A length control system comprising: a spool comprising (a) two opposing surfaces, substantially parallel to each other and rotatable around an axis, and (b) a center portion joining the two surfaces; a cover plate mounted to one of the two surfaces of the spool; a main line coiled around the center portion of the spool and extendable and retractable; a channel defined on the cover plate; and a switch configured to interact with the channel during extension or retraction of the main line from the spool, thereby restricting the extension of the main line to a predetermined length without restricting the retractability of the main line.
 8. The system of claim 7, wherein the length control system comprises two channels defined on one of the two surfaces.
 9. The system of claim 7, wherein the length control system comprises three channels defined on one of the two surfaces.
 10. The system of claim 7, wherein the switch is a pin configured to be inserted into the channel.
 11. The system of claim 7, wherein the switch is a manual switch mechanism.
 12. The system of claim 7, further comprising a manually actuated brake mechanism.
 13. A retractable leash device, comprising: a housing; and a length control system enclosed within the housing comprising: a spool comprising two opposing surfaces, substantially parallel to each other and rotatable around an axis, and a center portion joining the two surfaces; a main line coiled around the center portion of the spool and extendable and retractable; a channel defined on one of the two surfaces or on a cover plate mounted on one of the two surfaces; and a switch configured to interact with the channel during extension or retraction of the main line from the spool, thereby restricting the extension of the main line to a predetermined length without restricting the retractability of the main line.
 14. A method of restricting the movement of a human or animal comprising the steps of: attaching a leash device containing the leash control system of claim 1 to the human or animal; and engaging the switch in the channel to select a predetermined maximum length of the main line.
 15. A method of restricting the movement of a human or animal comprising the steps of: attaching a leash device containing the leash control system of claim 7 to the human or animal; and engaging the switch in the channel to select a predetermined maximum length of the main line. 